Being the old "codger" that I am and having been in the laboratory ventilation/containment for most of those years I can give some insight on the questions
being raised.

Years ago, OSHA came out with guidelines for fume hood face velocities to be between 60 - 125 LFPM. That is the equivalent of the state Highway Patrol recommending
60 - 125 MPH as a safe highway speed. Being in the business and being a certifier of fume hood, Biological Safety Cabinets and enclosures of all sorts I couldn't make much sense of that recommendation. But I did notice that some hoods contained better than
others at the same velocities. So what was the difference? They weren=E2=80™t all equal because of differences in geometries. As much as we would like to commoditize everything, different geometries, this include airfoil entrances, interior design and nuances of
airflow not visible to the naked eye were influencing performance.

When I founded Flow Sciences and began manufacturing containment devices and eventually fume hoods, I decided to utilize CFD(computational Fluid Dynamics) to
model the airflow on the inside of our designs. This was a remarkably eye opening and proved to be most helpful in maximizing the containment of the products.

I am telling this story to help those to understand that containment is not a number, but a design specifically incorporating all the engineering controls combined
with good laboratory practices that will produce the desired result. As a certifier I have seen high face velocities that performed poorly and low flow(60 - 80 LFPM) that performed remarkably well.

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